Cutter bit



Feb. 3, 1970 A. B. BOWER, JR 3,493,268

' CUTTER BIT Filed June 16, 1965 INVENTOR. ARNOLD B. BOWER,JR

BY WWW/M A T TORNEV United States Patent C) 3,493,268 CUTTER BIT ArnoldB. Bower, Jr., St. Clair Shores, Mich., assignor to General ElectricCompany, a corporation of New York Filed June 16, 1965, Ser. No. 464,370Int. Cl. E21c 13/00 U.S. Cl. 29986 2 Claims ABSTRACT OF THE DISCLOSURE Acutter bit having a generally cylindrical shank and a cutter tip mountedcentrally at both axial extremities of the shank. The center portion ofthe cutter bit contains a radially projecting shoulder encircling theshank, providing seating surfaces for the bit on both sides thereof, sothat the bit may be reversibly held in a block. Circumferential recessesbetween the shoulder and both cutter tips are adapted to receive holdingmeans to retain the bit in a block.

Cutter bit This invention relates to a cutter bit, and more specificallyto a cutter bit of the type used in mining machines.

Cutter bits of the type having a generally cylindrical shank and acutter tip mounted at a central axial extrimity of the shank are knownand have been used to advantage in mining machines. Such cutter bitspossess the advantage, as contrasted with rectangular bits in which thecutting tip is mounted radially offset from the central axis, of havingthe cutting forces operate through a larger cross section of both thebit body and the block in which it is mounted.

The principal object of the present invention is to provide a cutterbit, of the type having a generally cylindrical shank and a centrallylocated cutting tip, with cutting tips at both ends thereof so that thebit is reversible, thereby having approximately twice the life ofprevious cutter bits of this type but nevertheless retaining itsadvantages. Other objects will appear from the description of theinvention which follows.

The reversible cutter bit of the present invention comprises a generallycylindrical shank having cutting tips at its axial opposite ends and araised or projecting collar at its approximate axial midpoint. Thecollar provides dual seating or bearing surfaces for the cutter bit whenit is positioned in a block in which it is held. The shank contains twocircumferential recesses, one between each of the cutting tips and thecentral collar to receive a holding means for retaining the bit in ablock.

The invention will be more clearly understood from the followingdescription taken in connection with the accompanying drawing in whichFIGURE 1 is an elevational view, partially in section, of a block of thetype used in the mining of coal with the bit of the invention mountedfor operation therein;

FIGURE 2 is a side elevational view of the cutter bit shown in FIG. 1;and

FIGURE 3 is a fragmentary side elevational view showing an alternate tipdesign.

In the drawing, FIG. 1 shows a block 1 having a cylindrical bore 2 inwhich is mounted a reversible cutter bit 3 of the invention. The bit 3may form a relatively loose fit in the bore 2 for easy insertion andremoval of the bit and for rotation of the bit in the block duringoperation. The forward end of bore 2 is flared to provide a seating orbearing surface 4 for the corresponding bearing surface 5' (FIG. 2) ofthe bit. The cutter bit 3 is held in block 1 by means of a retention pin6 fitting a hole 7 through the block. A plurality of blocks of the typeshown in FIG. 1 may be attached to a mining machine in conventionalfashinon, as by welding or other suitable means.

As can be most clearly seen in FIG. 2, the cutter bit comprises agenerally cylindrical shank 8 having identical cutting tips 9 and 9' ofcemented tungsten carbide at axially opposite ends thereof. Shank 8 isconically tapered at 10 and 10' toward cutting tips 9 and 9'respectively at both ends of the shank. The central portion of the shankcontains a raised rim or collar 11 projecting annularly around the axialcenter of the cutter bit. The collar 11 is tapered radially on bothsides thereof to provide annular seating surfaces 5 and 5' for the bitWhen the bit is held in the block. As can be seen in FIG. 1, whencutting tip 9 is in operational position projecting from the block, theseating surface 5' most remote from tip 9 is utilized for seating thecutter bit in the block and, of course, seating surface 5 is used whenthe position of the cutter bit in the block is reversed to place cuttingtip 9" in operational position. A continuous curved circumferentialrecess 12 and 12' between the collar 11 and each tip 9 and 9'respectively is adapted to receive a holding pin to prevent removal ofthe bit from the block (as shown in FIG. 1).

The cutting tips may assume a variety of shapes. The exposed portion ofthe tips may be conical and terminate in a point or they may even becylindrical and terminate in a fiat cutting surface. The drawingillustrates two such shapes. As can be seen in FIGS. 1 and 2, theexposed portions of tips 9 and 9' are tetrahedral and contain aplurality of surfaces 13 and 13' which terminate in a sharp cuttingpoint 14 and 14' and which together form a generally tetrahedral shapedcutting tip at both ends of the shank. The base 15 and 15' of the tips 9and 9, which are brazed to the bit by conventional brazing techniques,are of cylindrical shape.

FIG. 3 illustrates an alternate tip shape in which the projectingportion of tip 16 is of hemispheroidal shape. The tip is otherwise thesame as tips 9 and 9 of FIGS. 1 and 2.

As will be noted from the drawing, the cutter bit is symmetrical .abouta plane radially bisecting the shank, i.e., a plane passingperpendicular to the axis of the bit through the center of collar 11 inFIG. .2. Such symmetry is of course necessary if the cutter bit is to betruly reversible in the block in which it is mounted to present twocutting tips in substantially identical operating position. As will alsobe noted from the drawing, the design of the bit is such that it is alsosymmetrical about a plane passing through the central axis of the bit.Such design is desirable to permit rotation of the bit in the blockduring cutting, or to permit utilization of the bit regardless of itsparticular position of rotation around its central axis when inserted inthe block.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A reversible cutter bit comprising a generally cylindrical shankhaving cutting tips at central axially opposite ends thereof, said shankbeing conically tapered at said opposite ends toward said cutting tips,

the central portion of said shank containing a radially projectingcollar encircling the shank, said coller being tapered radially on bothsides thereof to provide annular seating surfaces for the bit on bothsides thereof when the bit is held in a block,

said shank containing a continuous circumferential recess along acylindrical portion thereof between said collar and the conicallytapered portions of said shank to receive a holding pin adapted toretain said bit rotatably in a block,

said bit being symmetrical about both its central axis and a planeradially bisecting the shank, the shank being in the shape of a rightcylinder except for the conically tapered opposite ends thereof, thetapered radially projecting collar and the circumferential recess.

2. A bit member comprising: a body symmetrical about a centrallongitudinal axis and having an enlarged diameter region in about themiddle of the length thereof with tapered shoulders on opposite sides,the body on each side of said region being smaller in diameter than saidregion and including a cylindrical region operable to serve as asupporting shank for the bit member, the body on each end terminating ina point, an element harder than said body carried by said body at eachsaid point, a support block having a bore for receiving the shank of thebit member, and means for retaining such shank in said bore againstaxial movement therein while permitting free rotation of said body onsaid axis.

References Cited UNITED STATES PATENTS Krekeler 299-92 Krekeler 299-92Holmes 175-383 Simmons 299-93 Ellis et al. 175-383 Cummingham 175-410Krekeler 299-92 Snipe 299-91 US. Cl. X.R.

